Few companies have made as many important contributions to post-World War II American life as DuPont. Its scientists created Freon, allowing mass-market refrigerators and air conditioners; it invented nylon and the synthetic fibers Rayon and Lycra; and it churned out Teflon, a nonstick coating used on pots and pans. But DuPont also manufactured a number of dangerous chemicals, including fungicides and insecticides, rubber and industrial gases.

In the 1950s, as the company expanded its Teflon production, it started testing its chemical for safety. The test results were startling: Exposure to C8, which DuPont named after its chemical formula, led to enlarged livers in rats and rabbits. Later that decade, researchers asked a group of volunteers to smoke cigarettes laced with C8 and found that nine out of 10 became noticeably ill for an average of nearly nine hours, suffering from chills, backaches, fevers, coughing and more.

The company knew about these health risks, but it did not disclose them publicly, even as workers at the Parkersburg plant where the chemical was produced began reporting illnesses ranging from headaches to endocrine disorders. In the 1970s, as pressure mounted for government regulation of chemicals, DuPont and 3M negotiated the creation of the Toxic Substances Control Act, or TSCA, a landmark law that required companies to perform safety tests on new substances before they could be put on the market.

As a result, DuPont and 3M were able to block a key provision in TSCA that would have required such testing. That was a turning point in the fight to protect the environment and people from dangerous chemicals.